Ship propulsion system

ABSTRACT

A ship propulsion system comprising a mechanism to convert mechanical power into a swinging, paddle-like action of a fin-like plate, located at the exterior of a vessel, thereby mimicking the propulsion made by the tail of a fish.

INTRODUCTION AND BACKGROUND OF THE INVENTION

Current ship propulsion relies to a great extend on using different forms of rotating propellers in order to convert mechanical power into thrust.

This method is generally satisfactory. However, there are major drawbacks. First, their mechanical efficiency is generally low and typically does not exceed 70%. That means that typically one-third of the mechanical power input into the propeller shaft is converted into heating the water via a process of turbulence. This can readily be observed in the wake of high speed motor boats.

Secondly, the propeller speed is limited by a phenomenon called cavitation, where water vapor formed in a vacuum next to the propeller blade collapses further down stream, causing loss of efficiency, noise, and damage to the propeller's metal.

Third, propellers are inherently noisy. This effect is especially detrimental to submarines relying on stealth.

A similar, manual, propulsion system, using a form of a paddle, is exhibited in U.S. Pat. No. 6,709,306 by Brown, William Blake. His device was intended to amplify the thrust of a forearm and the device is not applicable to ship propulsion.

My invention tries to overcome the above mentioned deficiencies by providing a system that mimics the propulsion method of the tailfins of fish.

Some of us have observed dolphins racing along or even overtaking ocean liners. They seem to swim almost effortlessly, with no discernable wake left behind. This indicates a very high efficiency in the translation from muscle power to forward thrust. Fishes can regulate the speed of their forward motion by changing the angular excursion of their tails, and by changing the frequency thereof.

My invention also takes account of the need to vary the speed of a vessel, by being able to change the angle of excursion of my fishtail substitute.

Finally, it was observed, that there is a momentary pause in the motion of a fishtail following a power stroke. This allows the displaced water to settle down. How this is accomplished in my invention, and other explanations, are given in the following description of my invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional, central, view of a preferred embodiment of my invention, with the front portion of the depicted vessel removed.

FIG. 2 is a planar view of the embodiment shown in FIG. 1 with the second plate removed for clarity.

FIG. 3 is a schematic view of the linkage arrangement of my invention, depicting the relationship between the rotational input and the angular excursions, shown at its maximum setting.

FIG. 4 is a schematic view similar as in FIG. 3, with the linkage set to produce only one-half of the angular excursions.

DETAILED DESCRIPTION

Referring to FIG. 1, it shows a vessel 1, having an open hull 4, containing therein an engine 2, having a rotating output shaft 3 solidly connected to an arm 7, having a slotted opening 13, and, on one end receiving a pivot pin 8 connecting to a movable beam 9. Linkage pin 8, furthermore connects to a adjustable linkage consisting of an outer link 15 and an inner link 14, the latter being rotably connected to shaft 3.

Any rotation of link 14 vis-a-vis shaft 3 causes to pivot pin 8 to slide within slot 13 and thereby alter the radial distance between pin 8 and shaft 3. This, in turn, causes a change in the excursion of beam 9.

Beam 9, after exciting the hull 4 of the vessel, connects to another arm 10 via a pin 17. The latter is slidingly arranged in a slotted opening 12 being part of beam 9.

Arm 10 in turn is fixedly connected to a shaft 6, being part of a plate 5. This plate is supported, together with shaft 6 by a support bracket 18. The latter being suitably fastened to the hull of the vessel.

Any outward movement of beam 9 will cause pin 17 to slide a given distance along slot 12 and, thereafter, rotating arm 10 in a clockwise direction. This, in turn, causes arm 5 to swing across an arc, defined by twice the angle α.

Plate 5 furthermore, has attached to it a second plate 11, able to swing freely around a shaft 19 over a distance defined by twice the angle β. The amount of rotation in either direction is limited by a pre-defined stop 16.

The function of my proposed mechanism will be better understood when viewing FIGS. 3 and 4.

FIG. 3 shows the distance RI (between pivot point 8 and rotating shaft 3) at its maximum. Neglecting, for simplicity, the loss of motion by pin 17 in slot 12, we can see, that when pivot pin is in an outer, horizontal plane (labeled A), beam 9 is fully extended. This causes plate 5 to swing fully in the clockwise direction to point A. Upon rotation of shaft 3 to an upper, vertical direction (B), plate 5 now assumes a neutral, horizontal position B. Upon further rotation to point C, the plate 5 now swings in the opposite direction indicated as C. Continuing the rotation of shaft 3 to point D will reverse the swinging motion of plate 5 towards a neutral, horizontal position again (D); thereafter, the former actions begin anew.

FIG. 4 depicts a setting of pin at a distance R2, being half the distance shown in FIG. 3. While actions between rotation of pivot pin 8 and the following excursions of plate 5 between locations A to D are identical, the resultant angular excursions of plate 5 now is only one half the angular distance. This causes a greatly reduced output of mechanical power than the configuration shown in FIG. 3, causing the speed of propulsion to decrease, as shall be explained below.

The Power conversion used to convert mechanical power into a propulsion force can best be understood from the following example;

Assuming a plate 5, having an effective area A of 1 square feet and a length L of 1.5 feet, of which ⅔rds being the average effective length. Assuming further, that the velocity of movement of the plate U is 10 feet per second. Note, that the max. plate velocity is obtained when the plate is at the max. angle α corresponding to a position of pivot point of B or D, and while the plate is swinging towards the center position. Since only a portion of the displaced water is pushed backwards, we have to multiply the force by the sinus of the angle α, here assumed to be 40 degrees. The density of water ρ is assumed to be 62 pound per cubic feet.

From the above, and neglecting efficiencies, we have:

Horse Power=A×⅔ L×U×sin α×ρ/78.

This yields, for the above example, 5.1 Horse Power.

The reaction force which propulses the ship is given as:

F=Mass×Velocity²

Where the mass is: A×⅔L×ρ×sin α/2×32.1=0.62 lbs s²/ft, This makes F=0.62×10²=62 lbs.

It is now recognized, that when the distance R2 between pivot point 8 and shaft 3 is reduced in half, then the plate velocity at ⅔ L is also only one half. This then makes the horse power requirements only 1.4 HP, or, only 27% of what is needed for the max. R1 setting.

This also reduces the mass moved to only 0.16 lbs s²/ft. and the resulting force F to 8 lbs. It can be seen, that a reduction of the beam 9 movement by 50% can yield a force reduction down to 13%, or over a ratio of about 8:1. This shows the great effectiveness of using an adjustment of the lever ratio as a means for speed control of a ship.

The following is a discussion of the purpose of the override provided by slot 12 in beam 9. Its functions to stop the movement of plate 5 momentarily, once a max excursion of plate 5 is reached in either direction. This will allow time to move arm 7 towards a near vertical position (either up or down), where it can accomplish the highest angular velocity, hence the maximum power input on beam 9 and therefore on plate 5. Conversely, when arm 7 is in a nearly horizontal position, there will be little movement and velocity of beam 9. This is when plate 5 in each respective maximum position following a power stroke.

A power stroke here is defined where arm 7 travels +/−45 degrees from positions B or D. Here beam 9 achieves the highest velocity.

A second, movable plate is swingingly attached to the end of plate 5, by means of an axel 19. The swinging motion of plate 11 is restricted at typically 45 degrees from the longitudinal axis of plate 5. Any further excursion is limited by stops 16. The purpose of plate 11 is as follows: During each power stroke of plate 5 (towards the center) there will be resistance by the water. This resistance pressure now forces plate 11 to swing in the opposite direction of plate 5 movement, till the stops 16 limited the tilting, This causes the plate to exert an opposite pressure on the water in contact, thereby helping in the propulsion effort aided by the greater contact angle (angle α plus angle β) than provided by plate 5 alone. The greater angle plus the greater distance between plate 11 and shaft 6 now allow for a greater power conversion than previously discussed.

While the invention has been discussed in a preferred embodiment, nothing shall preclude additional modifications without departing from the scope of the following claims. For example, instead of providing a slot in beam 9, such means of override can also be provided in arm 10. It may also be advisable to make beam 9 adjustable in length, to aid in calibration. Further more, instead of having a rotating linkage arrangement, pivot point 8 may also be distance adjusted by means of a motor driven screw. 

1. A Ship Propulsion System comprising a vessel 1 having one or more engines 2 with a rotary output shaft 3 placed inside the hull 4 of said vessel, a movable first plate 5 having a fixed rod end 6 being suitably fastened to the rear of the vessel, an first arm 7 fastened to the rotating output shaft 3 on one end and, by means of linkage pin 8, to a beam 9 on the other end, said beam extending to the exterior of said hull and connecting there to one end of a second arm 10 whose other end is fixedly connected to the shaft 6 attached to said first plate 5 whereby each rotation of the engine shaft 3 will cause a back-and-forth swinging motion of said plate
 5. 2. A Ship Propulsion System as in claim 1, wherein said first plate 5 having a movable second plate 11 attached to its outer extremity.
 3. A Ship Propulsion System as in claim 1, wherein the angular excursion α of the first plate 5 is limited to between 0 and 50 degrees from the centerline of said vessel in either direction.
 4. A Ship Propulsion System as in claim 2, wherein the angular excursion β of the second plate 11 in respect to the longitudinal axis of said first plate 5 is limited to between 0 and 50 degrees in either direction.
 5. A Ship Propulsion System as in claim 1, wherein the distance L between the center of said rotating shaft 3 and the center of said linkage pin 8 of said beam 9 can be varied.
 6. A Ship Propulsion System as in claim 1, wherein said beam 9 is slotted 12 allowing the second arm 10 to move a pre-determined distance to temporarily stop the swinging motion of said plate 5 even while the output shaft 3 of the engine 2 is still rotating.
 7. A Ship Propulsion System as in claim 1, wherein said first arm 7 is partly slotted allowing the linkage pin 8 of said beam 9 to be moved towards or away from the rotating shaft 3 in order to vary the amount of excursion of the beam 9 for each rotation of said shaft
 3. 8. A Ship Propulsion System as in claim 7, wherein the means to vary the distance between the linkage pin and said rotary shaft comprise two angularly interconnected links 14, wherein one end of one of the links 14 is slidingly connected to said rotating shaft 3, while the end of the second link 15 is connected to the linkage pin 8 of said beam
 9. 9. A Ship Propulsion System as in claim 2, wherein pin 6 and plates 5 and 11 are supported by a bracket 18 being suitably attached to the rear of the vessel. 10, A Ship Propulsion System as in claim 4, wherein the plate 11 has attached thereto a stop 16, able to interact with plate
 5. 